The present invention relates to a method for caloric nystagmus testing. More particularly, the present invention relates to improvements which simplify the inducing of nystagmus and greatly expand the practical utility of caloric nystagmus testing.
Nystagmus is a regular, alternating eye movement of variable velocity which can be induced by many known methods. It is well-recognized that by monitoring controllably-induced nystagmus a diagnostician can ascertain various vestibular disorders as well as other isolated clinical pathology as may pertain to various medico-surgical subspecialties. Measurement of nystagmus can be done visually or by electronic apparatus, either of which may be employed in conjunction with the present invention.
Caloric nystagmus testing involves the injection of specified fluid volumes at known temperatures into the patient's ear to induce a nystagmus response. The most widely used fluid for caloric testing is water. However, water necessarily overflows the patient's ear, is uncomfortable for the patient, is messy to handle, and requires much maintenance. Further large amounts of water are required, all of which must be heated from ambient temperature to specific temperatures above ambient. Air has also been used as a caloric test fluid but often causes undue patient discomfort; furthermore, variability of test results have been observed due in part to the lower heat capacity of air and sensitivity to applicator positioning. Open (i.e. overflowing) water caloric testing is medically contraindicated for patients having: a hole in the ear drum; an ear infection; a prior surgically-created cavity in the ear; or middle ear ventilating tubes.
It is an object of the present invention to provide a method for conducting caloric tests without the aforementioned disadvantages.
It is another object of the present invention to provide a method for conducting caloric tests without requiring injection of fluid directly into the ear.
It is still another object of the present invention to provide a method of conducting caloric nystagmus tests without flowing air or water directly into the patient's ear.
It is still another object of the present invention to provide an energy-conserving technique for inducing nystagmus, saving on both water and heating consumption.
There has been some suggestion in the prior art that caloric testing can be performed by the finger-cot method whereby a balloon-like member is inserted in the ear and the test liquid is caused to flow into that member. In practice, however, it has been found that introduction of the balloon-like member into the ear is extremely difficult; moreover, the measurement has proven highly insensitive and many of the disadvantages of direct flow into the ear (mess, undue pressure build-up, etc.) remain. Further, there is a danger that the finger-cot, when expanded, will be too deep within the ear canal, resulting in damage to the tympanic membrane from pressure build-up.
It is a further object of the present invention to provide a method for performing caloric nystagmus tests without the need for directly flowing test fluid into the ear and without the disadvantages of the finger-cot approach.